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Medical Research
Women's Health

An Unexpected Benefit of Progesterone?

The female hormone progesterone, widely used in birth control, appears to ward off the worst effects of influenza and may also help damaged lung cells to heal more quickly, researchers have found in an animal study.

The findings, by researchers from the John Hopkins Bloomberg School of Public Health, were published in PLOS Pathogens.

The World Health Organization reports that more than 100 million young adult women around the world are on progesterone-based contraception. And women of reproductive age are twice as likely as men to suffer from complications related to the influenza virus.

“Despite the staggering number of women who take this kind of birth control, very few studies are out there that evaluate the impact of contraceptives on how the body responds to infections beyond sexually transmitted diseases,” says study leader Sabra L. Klein, PhD, an associate professor in the Bloomberg School’s Department of Molecular Microbiology and Immunology. “Understanding the role that progesterone appears to play in repairing lung cells could really be important for women’s health. When women go on birth control, they don’t generally think about the health implications beyond stopping ovulation, and it’s important to consider them.”

The World Health Organization (WHO) has already listed hormonal contraceptives as an essential medication because of the profound benefits these compounds can have on women’s health by widening the interval between pregnancies, including decreased rates of maternal mortality and improved outcomes for babies and children.

For their research, Klein and her colleagues placed progesterone implants in female mice and left other mice, also female, without. The mice were then infected with influenza A virus. Both sets of mice became ill, but those with implants had less pulmonary inflammation and better lung function and saw the damage to their lung cells repaired more quickly.

The researchers found that progesterone was protective against the more serious effects of the flu by increasing the production of a protein called amphiregulin by the cells lining the lungs. When the researchers bred mice that were depleted of amphiregulin, the protective effects of progesterone disappeared as well. Klein says she was not surprised that progesterone lessened the inflammation and damage associated with the flu. What she didn’t expect was to find that progesterone also helped induce repair.

When female mice (and possibly humans) get sick with the flu, their natural levels of progesterone fall. Women on hormonal contraceptives – be it a birth control pill, intrauterine device (IUD) or injection – get a steadier level of progesterone, which overrides what the ovaries make naturally or what the virus takes away during infection.